security: fix code/command injection in calculators, WP downloader, and KV store

[devin-ai-integration]

Summary

Fixes the critical code-/command-injection findings from a security scan of the repo. Each fix preserves the original intended behavior; only the unsafe evaluation/execution path is replaced.

1. ai-terminal-assistant/main.py — arbitrary code execution (RCE)
The calc command ran eval(value) on raw user input, so e.g. calc __import__("os").system("...") executed arbitrary code. Replaced with an ast-based safe_eval() that only allows numeric literals and arithmetic operators (+ - * / // % **, unary +/-); anything else raises ValueError.

2. gui-calculator/Calculator.py — arbitrary code execution
equate() ran eval(display.get()). Replaced with the same safe_eval() and wrapped in a try/except that shows Error instead of crashing on bad input.

3. wordpress_plugin_downloader/downloader.py — OS command injection

- os.system("axel -a -n 16 %s && unzip %s" % (link, filename))
+ subprocess.run(["axel", "-a", "-n", "16", link], check=True)
+ subprocess.run(["unzip", filename], check=True)

link/filename came from scraped page HTML and were interpolated into a shell string. Now passed as argument lists with no shell, so metacharacters can't inject commands.

4. KeyValueStore/db.sh — arbitrary command execution + regex injection
The script ended in $@, which executed any function or command name passed as the first argument (e.g. db.sh 'x; touch INJECTED'). It also used unquoted grep -e $1 / sed "s/$1.../", allowing regex/argument injection. Rewritten to:

• Dispatch via an explicit case allow-list (create|read|update|delete) instead of $@.
• Quote all variable expansions.
• Match keys exactly with awk '$1 == key' (passing the key via -v) instead of grep/sed regexes.

Notes / not fixed

• BasicCalculator/script.js uses client-side eval() on the user's own input (self-contained, no server/other-user exposure) — flagged as low risk, left as-is.
• No real hardcoded secrets were found in first-party code — matches were placeholders (YOUR_API_KEY, <your consumer secret>) or env-var lookups. The only real token is in a committed third-party node_modules file (todolist/node_modules/debug/.coveralls.yml).
• Committed node_modules (Make-Text-Uppercase, todolist) are outdated and a supply-chain concern, but out of scope for this focused fix.

Verification

• python3 -m py_compile passes for all changed Python files.
• safe_eval("2+3*4") → 14; injection payload raises ValueError.
• db.sh create/read/update/delete round-trips correctly; injection payload is rejected with a usage error.

Link to Devin session: https://app.devin.ai/sessions/53e420bb2b644c55bffeeb860fd69155
Requested by: @josharsh

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